An important consideration of any potential replacement, filament or LED, is the measure called "light center length." The distance from bottom of bulb base to the center of the light producing medium. That has to match the required focal position of the reflector or you'll get some weird patterns out of the headlight. This would make an LED replacement difficult because getting enough lumens would require a LOT of LEDs and packing those into the required location would seem to be a daunting task for a lamp designer. I think the practical solution here is still the incandescent filament.

If a 200P25 32V is still available, that may be the best bet. With a 14" reflector behind it the difference in output may not be as significant as you might think. Consider how much light comes out of those 200W PAR56 sealed beam loco headlight bulbs, plus you'd have that larger reflector with which to work.

David H. Hamley

Post subject: Re: 250P25 32V Locomotive Headlight Bulbs

Posted: Fri Jan 09, 2015 1:55 pm

Joined: Tue Aug 24, 2004 3:07 pmPosts: 669

A bit more info on loco headlight bulbs: I have consulted my 1988 edition of the GE lamp catalog to see what was listed even then, let alone 2015.

Only two 32V headlight bulbs are shown. Lamp 100A21/3 32V is a 100W medium screw base clear bulb with the familiar pear shape and a maximum diameter of 21 eights of an inch. It produces 1610 lumens and has a rated life of 500 hours when burned at rated voltage. Another important measurement is the "light center length" of 3.00". Thus would typically be used in the smaller reflectors on industrial locos. (The headlights on Pennsylvania Trolley Museum's 1942 Porter center-cab have 10" reflectors and the original parts book calls for the 100W lamp.)

The other listing is for the 250P25 32V that is the subject of this thread. In this case the clear bulb is 25 eights of an inch diameter and is more of a round shape, which is what the letter P implies. This one produces 4650 lumens, also for a 500 hour life. The light center length is also 3.00".

The type of filament in both types is a tightly concentrated version, to put most of the light output right at the focus of the reflector. By implication, using any bulb with a different LCL would result in a different beam pattern.

Light Center Length, LCL, is measured from the tip of the center contact of the screw base to the center of light output of the filament. It should be noted that on certain older versions of headlight bulbs, a prefocus bayonet type base was used. In this case the LCL was measured from the TOP of the bayonet flanges, not from the tip of the bulb base. This means that converting a headlight that required the prefocus type bulb also means relocating the replacement screw socket to account for that different LCL measurement.

There was no listing for a 200W 32V headlight bulb in 1988, at least not in the GE catalog, which is about as comprehensive as they got.

There were also "Rebased" bulbs, with a bayonet base forced over the medium screw base. I think they were 250 Watt.

RCD

Post subject: Re: 250P25 32V Locomotive Headlight Bulbs

Posted: Sat Jan 10, 2015 12:10 pm

Joined: Fri Oct 24, 2008 9:05 pmPosts: 787Location: MA

Use three car headlight bulbs hooked up in searies for the time being.

EDM

Post subject: Re: 250P25 32V Locomotive Headlight Bulbs

Posted: Sat Jan 10, 2015 7:36 pm

Joined: Sun Aug 22, 2004 9:54 amPosts: 850Location: NJ

RCD, how are you going to make three AUTO headlight bulbs look like one of the correct LOCOMOTIVE headlight bulbs, centered in a 14 inch reflector? And how are you going to get the correct focus? What's next, Mag-Lite flashlights, duct taped to handrails instead of ditch lights? Get real...

Essentially all of the LED info in this thread is dead wrong. I won't get into point-by-point because it would be pedantic and off-topic. Most if it seems to be stereotypes established by the junk sold by Feit Electric, Lights of America and Chinese brand-of-the-week, marketed (skillfully!) for impulse purchase (on price) at the local big-box store. Price-point is the singular goal of these products, and they throw reliability, brightness and efficiency under the bus to get it. LEDs are better than that. Really.

Mark D.

Post subject: Re: 250P25 32V Locomotive Headlight Bulbs

Posted: Sun Jan 11, 2015 4:21 pm

Joined: Sun Aug 22, 2004 3:24 pmPosts: 169Location: Litchfield, MN.

Incandescent light bulbs are pretty much all made using the same technology. That means that the claim that the 'glue' that holds the base to the glass envelope will come loose and allow the vacuum to escape isn't correct. Light bulbs, just like vacuum tubes, are entirely sealed at the glass envelope. That 'glue' mentioned only holds the base to the lamp envelope itself. Generally speaking, the vacuum holds until the envelope breaks. It's not uncommon to find light bulbs from the 1920s that still work, and this shouldn't be any different for the locomotive light bulbs in this topic.

So something else must have caused the failures.

Has anyone thought to look in China? Last I heard, they were still running a few steam engines in mining and short line use. Even if that's all gone by now too, they just might have light bulbs there that will match the 250P25 32V lamp in this topic.

Buy a dozen for one good one that will work for a while.

Mark D.

crij

Post subject: Re: 250P25 32V Locomotive Headlight Bulbs

Posted: Wed Jan 14, 2015 8:19 pm

Joined: Sun Aug 22, 2004 12:15 amPosts: 525

Related but slightly off topic:

Has anyone found a source for the 64V version of these bulbs (e26 threaded base, 250W)? These were used in the 10"-12" reflector early diesels (44 tonner and larger). At the Ct Eastern RR Museum we have a 44 ton GE with 10" P/N glass reflectors, and we really don't want to put a PAR56 inside the reflector.

Hoboken Manufacturers - Hoboken Shore #700, later McHugh Bros. Line / New Hope & Ivyland - Tyburn Railroad #400 used 60 Volt, 250 Watt medium screw base headlights with a resistor to run on the 64 Volts of battery charged at 73.6 Volts. When the resistor broke, resistors from a more modern Diesel with 32 Volt headlights and 64 Volts of battery charged at about 72 Volts were substituted. Slight problem, if you reduce the Voltage and the Wattage stays the same, the Amperage increases. The headlight circuit breaker that could handle both 60 Volt, 250 Watt headlights at once would trip if both 32 Volt, 250 Watt headlights were lit at the same time. Tyburn did have some of the 60 Volt bulbs left over in stock back in 2011.

RCD

Post subject: Re: 250P25 32V Locomotive Headlight Bulbs

Posted: Thu Jan 15, 2015 10:37 pm

Joined: Fri Oct 24, 2008 9:05 pmPosts: 787Location: MA

EDM wrote:

RCD, how are you going to make three AUTO headlight bulbs look like one of the correct LOCOMOTIVE headlight bulbs, centered in a 14 inch reflector? And how are you going to get the correct focus? What's next, Mag-Lite flashlights, duct taped to handrails instead of ditch lights? Get real...

Mark D is correct, the glue is only to hold the bulb to the base. Something else is wrong and I would not be screwing hard to find bulbs in one after another just to watch them blow out. One caveat. Sometime ago the Chinese bulbs were causing problems, blowing out and starting electrical fires.

Try Ebay, occasionally NOS 250/34 bulbs show up. I managed to purchase a sizeable amount of these GE bulbs for under 20 each. I should have purchased everyone he offered. Sorry, I am not selling.

sousakerry

Post subject: Re: 250P25 32V Locomotive Headlight Bulbs

Posted: Wed Oct 14, 2015 10:12 am

Joined: Tue Sep 22, 2015 12:36 pmPosts: 197

Did anyone ever come up with a solution on this? We are down to our last two bulbs 100A21/3 32V on our 44 tonner at Southern Michigan Railroad Society. Last weekend I had to salvage one from unit 10 that is stored OSS.

We would really like to keep the 75 original and not do a sealed beam replacement.

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